Calculating earthquake force
Publish: 2021-04-10 03:57:04
1. Earthquake load: (DI Zhen He Zai) earthquake load (seismic force)
also known as earthquake force. Inertial force, earth pressure and water pressure on structures e to earthquake. Since the horizontal vibration has the greatest influence on buildings, only the horizontal vibration is considered
calculation formula of seismic force: seismic force = self weight × Seismic coefficient
compared with steel-concrete structure, the self weight of all steel structure is lighter, which is about two-thirds or one-half of that of steel-concrete structure. According to the above calculation method, the steel structure building with light weight will greatly rece the seismic force, relieve the seismic force and protect the stability of the whole building.
also known as earthquake force. Inertial force, earth pressure and water pressure on structures e to earthquake. Since the horizontal vibration has the greatest influence on buildings, only the horizontal vibration is considered
calculation formula of seismic force: seismic force = self weight × Seismic coefficient
compared with steel-concrete structure, the self weight of all steel structure is lighter, which is about two-thirds or one-half of that of steel-concrete structure. According to the above calculation method, the steel structure building with light weight will greatly rece the seismic force, relieve the seismic force and protect the stability of the whole building.
2. Seismic force = self weight × Seismic coefficient
3. 1 Understanding and application of the ratio of seismic force to seismic interlayer displacement
(1) code requirements: articles 3.4.2 and 3.4.3 of the code for seismic design and article 4.4.2 of the code for design of high rise buildings stipulate that the lateral stiffness of the floor should not be less than 70% of the lateral stiffness of the upper adjacent floor or 80% of the average lateral stiffness of the upper adjacent three floors< (2) calculation formula: ki = VI/ Δ UI
3 scope of application:
① it can be used to calculate the engineering stiffness ratio specified in article 3.4.2 and 3.4.3 of the code for seismic design and article 4.4.2 of the code for seismic design< It can be used to judge whether the basement roof can be used as the embedded end of the superstructure< (2) understanding and application of shear stiffness (1) code requirements:
Article e.0.1 of the code for design of high rise buildings stipulates that when the large space at the bottom is one floor, the equivalent shear stiffness ratio of the upper and lower structures of the transfer floor can be adopted approximately γ It represents the change of stiffness of upper and lower structure of transfer floor, γ It should be close to 1 in non seismic design γ It should not be more than 3. In seismic design γ It should not be greater than 2. See page 151 of the code for design of tall buildings for calculation formula< (2) article 6.1.14 of the code for seismic design stipulates that when the basement roof is used as the embedded part of the superstructure, the ratio of the lateral stiffness of the basement structure to that of the superstructure should not be less than 2. The calculation method of the lateral stiffness can adopt the shear stiffness according to the provisions. The calculation formula is shown on page 253 of seismic code< (2) the calculation method provided by SATWE software is the method provided by seismic code< (3) application scope: it can be used to calculate the stiffness ratio of the project specified in article e.0.1 of the code for design of high rise buildings and article 6.1.14 of the code for seismic design< (3) understanding and application of shear bending stiffness (1) code requirements:
Article e.0.2 of the code for design of high rise buildings stipulates that when the large space at the bottom is more than one floor, the equivalent lateral stiffness ratio of the upper part of the transfer floor to the lower part of the structure shall be calculated γ E can be calculated by formula (e.0.2) using the calculation model shown in Figure E. γ E should be close to 1 in non seismic design γ E should not be greater than 2, when seismic design γ E should not be greater than 1.3. For the calculation formula, see page 151 of the code for design of tall buildings< (2) article e.0.2 of the code also stipulates that when the transfer floor is set at three or more floors, the floor lateral stiffness ratio shall not be less than 60% of the adjacent upper floors< (2) calculation method adopted by SATWE software: simplified calculation of high lateral displacement stiffness
3) application scope: it can be used to calculate the stiffness ratio of Engineering specified in article e.0.2 of the code for design of tall buildings< (4) the main differences between the application scope of stiffness ratio in Shanghai code and national code are as follows:
(1) article 6.1.19 of Shanghai Code stipulates that the lateral stiffness of basement floor should not be less than 1.5 times of that of upper floor when the basement is used as the embedded end of superstructure< (2) the shear stiffness ratio has been used to calculate the three stiffness ratios in Shanghai code< (5) engineering example:
(1) project overview: a project is a frame supported shear wall structure, with 27 floors (including two floors of basement), and the sixth floor is a frame supported transfer floor. The three-dimensional axonometric drawing, the sixth and seventh floor plan of the structure are shown in Figure 1 (the figure is omitted). The seismic fortification intensity of the project is 8 degrees, and the design basic acceleration is 0.3g.
the calculation results of X-direction stiffness ratio of 1-13 floors:
e to the difficulty in listing, the meaning of each line of numbers below is as follows: the calculation method of three kinds of stiffness is separated by "/", the first section is the algorithm of seismic shear force and seismic interlayer displacement ratio, and the second section is shear stiffness, The third section is shear bending stiffness. The specific data are: layer number, RJX, ratx1, weak layer / RJX, ratx1, weak layer / RJX, ratx1, weak layer
where RJX is the lateral stiffness of the tower in the overall coordinate system of the structure (it should be multiplied by the 7th power of 10); Ratx1 is the smaller of the ratio of the lateral stiffness of the tower on this floor to 70% of the lateral stiffness of the corresponding tower on the upper floor or 80% of the average stiffness of the upper three floors. The specific data are as follows:
1, 7.8225, 2.3367, no / 13.204, 1.6408, no / 11.694, 1.9251, no
2, 4.7283, 3.9602, no / 11.444, 1.5127, no / 8.6776, 1.6336, no
3, 1.7251, 1.6527, no / 9.0995, 1.2496, no / 6.0967, 1.2598, no
4, 1.3407, 1.2595, no / 9.6348, 1.0726, No / 6.9007, 1.1557, no
5, 1.2304, 1.2556, no / 9.6348, 0.9018, yes / 6.9221, 0.9716, yes
6, 1.3433, 1.3534, no / 8.0373, 0.6439, yes / 4.3251, 0.4951, yes
7, 1.4179, 2.2177, no / 16.014, 1.3146, no / 11.145, 1.3066, no
8, 0.9138, 1.9275, no / 16.014, 1.3542, No / 11.247.1.3559, no
9, 0.6770, 1.7992, no / 14.782, 1.2500, no / 10.369, 1.2500, no
10, 0.5375, 1.7193, no / 14.782, 1.2500, no / 10.369, 1.2500, no
11, 0.4466, 1.6676, no / 14.782, 1.2500, no / 10.369, 1.2500, no
12, 0.3812, 1.6107, no / 14.782, 1.2500, No / 10.369, 1.2500, no 13, 0.3310, 1.5464, no / 14.782, 1.2500, no / 10.369, 1.2500, no
note 1: when SATWE software calculates "seismic shear force and seismic interlayer displacement ratio", fill in "0" in "relative stiffness ratio of backfill to basement restraint" in "basement information"
note 2: the number of weak layers and corresponding layer number are not defined separately in SATWE software
note 3: this example is mainly used to illustrate the realization process of the three stiffness ratios in SATWE software, and the rationality of the structural scheme is not discussed< (3) analysis of calculation results (1) the judgment results of weak layer are different when stiffness ratio is calculated by different methods
② in the "adjustment information" of SATWE software, the designer should specify the number of the sixth weak layer of the conversion layer. The designation of weak layer number does not affect the program's automatic judgment of other weak layers
③ when the transfer floor is set at three or more floors, the height regulation also stipulates that the lateral stiffness ratio of the floor should not be less than 60% of the adjacent upper floor. This SATWE software has no direct output results, so designers need to calculate the stiffness of each layer separately according to the program output. For example, the calculation results of this project are as follows:
1.3433 × 107／1.4179 × 107＝94.74％> 60%
meet the specification requirements< (4) whether the basement roof can be used as the embedded end of the superstructure:
A) the ratio of seismic shear force to seismic interlayer displacement
= 4.7283 × 107／1.7251 × The basement roof can be used as the embedded end of the superstructure
b) the shear stiffness ratio
= 11.444 × 107／9.0995 × (107) = 1.25 < 2
the roof of the basement can not be used as the embedded end of the superstructure
⑤ when SATWE software calculates the shear bending stiffness, the value range of H1 includes the height of the basement, and the height of H2 is equal to or less than H1. For the designers who want the value of H1 to be taken from 0.00 or above, or remove the basement and recalculate the shear bending stiffness, or manually calculate the stiffness ratio according to the shear bending stiffness output by the program. Taking the project as an example, H1 is calculated from 0.00, using the stiffness string model, the calculation results are as follows:
the floor number of the transfer floor is 6 (including basement), the starting and ending floor number of the lower part of the transfer floor is 3-6, H1 = 21.9m, the starting and ending floor number of the upper part of the transfer floor is 7-13, h2 = 21.0m.
K1 = [1 / (1 / 6.0967 + 1 / 6.9007 + 1 / 6.9221 + 1 / 4.3251)] × 107=1.4607 × 107
K2=[1/1/11.145+1/11.247+1/10.369 × 107=1.5132 × 107
Δ 1=1/K1 Δ 2 = 1 / K2
then shear bending stiffness ratio γ e= Δ one × H2/ Δ two × (6) discussion on the properties of three kinds of stiffness ratio
(1) ratio of seismic shear force to seismic interlayer displacement: a calculation method related to external force. Specified in the specification Δ UI includes not only the displacement caused by seismic force, but also the displacement caused by overturning moment Mi of the floor and the rigid body rotation displacement of the floor caused by the rotation of the next floor< (2) shear stiffness: the calculation method is mainly the ratio of shear area to the corresponding storey height, which is closely related to the shear area and storey height of vertical members. However, the shear stiffness does not consider the influence of the structural system with braces and the height of shear wall openings< (3) shear bending stiffness: actually, it is the interlayer displacement angle under the action of unit force, and its stiffness ratio is also the ratio of interlayer displacement angle. It can consider the influence of shear deformation and bending deformation at the same time, but does not consider the constraints of upper and lower layers
the properties of the three kinds of stiffness are completely different, and there is no necessary connection between them. Because of this, the code gives them different scope of application.
(1) code requirements: articles 3.4.2 and 3.4.3 of the code for seismic design and article 4.4.2 of the code for design of high rise buildings stipulate that the lateral stiffness of the floor should not be less than 70% of the lateral stiffness of the upper adjacent floor or 80% of the average lateral stiffness of the upper adjacent three floors< (2) calculation formula: ki = VI/ Δ UI
3 scope of application:
① it can be used to calculate the engineering stiffness ratio specified in article 3.4.2 and 3.4.3 of the code for seismic design and article 4.4.2 of the code for seismic design< It can be used to judge whether the basement roof can be used as the embedded end of the superstructure< (2) understanding and application of shear stiffness (1) code requirements:
Article e.0.1 of the code for design of high rise buildings stipulates that when the large space at the bottom is one floor, the equivalent shear stiffness ratio of the upper and lower structures of the transfer floor can be adopted approximately γ It represents the change of stiffness of upper and lower structure of transfer floor, γ It should be close to 1 in non seismic design γ It should not be more than 3. In seismic design γ It should not be greater than 2. See page 151 of the code for design of tall buildings for calculation formula< (2) article 6.1.14 of the code for seismic design stipulates that when the basement roof is used as the embedded part of the superstructure, the ratio of the lateral stiffness of the basement structure to that of the superstructure should not be less than 2. The calculation method of the lateral stiffness can adopt the shear stiffness according to the provisions. The calculation formula is shown on page 253 of seismic code< (2) the calculation method provided by SATWE software is the method provided by seismic code< (3) application scope: it can be used to calculate the stiffness ratio of the project specified in article e.0.1 of the code for design of high rise buildings and article 6.1.14 of the code for seismic design< (3) understanding and application of shear bending stiffness (1) code requirements:
Article e.0.2 of the code for design of high rise buildings stipulates that when the large space at the bottom is more than one floor, the equivalent lateral stiffness ratio of the upper part of the transfer floor to the lower part of the structure shall be calculated γ E can be calculated by formula (e.0.2) using the calculation model shown in Figure E. γ E should be close to 1 in non seismic design γ E should not be greater than 2, when seismic design γ E should not be greater than 1.3. For the calculation formula, see page 151 of the code for design of tall buildings< (2) article e.0.2 of the code also stipulates that when the transfer floor is set at three or more floors, the floor lateral stiffness ratio shall not be less than 60% of the adjacent upper floors< (2) calculation method adopted by SATWE software: simplified calculation of high lateral displacement stiffness
3) application scope: it can be used to calculate the stiffness ratio of Engineering specified in article e.0.2 of the code for design of tall buildings< (4) the main differences between the application scope of stiffness ratio in Shanghai code and national code are as follows:
(1) article 6.1.19 of Shanghai Code stipulates that the lateral stiffness of basement floor should not be less than 1.5 times of that of upper floor when the basement is used as the embedded end of superstructure< (2) the shear stiffness ratio has been used to calculate the three stiffness ratios in Shanghai code< (5) engineering example:
(1) project overview: a project is a frame supported shear wall structure, with 27 floors (including two floors of basement), and the sixth floor is a frame supported transfer floor. The three-dimensional axonometric drawing, the sixth and seventh floor plan of the structure are shown in Figure 1 (the figure is omitted). The seismic fortification intensity of the project is 8 degrees, and the design basic acceleration is 0.3g.
the calculation results of X-direction stiffness ratio of 1-13 floors:
e to the difficulty in listing, the meaning of each line of numbers below is as follows: the calculation method of three kinds of stiffness is separated by "/", the first section is the algorithm of seismic shear force and seismic interlayer displacement ratio, and the second section is shear stiffness, The third section is shear bending stiffness. The specific data are: layer number, RJX, ratx1, weak layer / RJX, ratx1, weak layer / RJX, ratx1, weak layer
where RJX is the lateral stiffness of the tower in the overall coordinate system of the structure (it should be multiplied by the 7th power of 10); Ratx1 is the smaller of the ratio of the lateral stiffness of the tower on this floor to 70% of the lateral stiffness of the corresponding tower on the upper floor or 80% of the average stiffness of the upper three floors. The specific data are as follows:
1, 7.8225, 2.3367, no / 13.204, 1.6408, no / 11.694, 1.9251, no
2, 4.7283, 3.9602, no / 11.444, 1.5127, no / 8.6776, 1.6336, no
3, 1.7251, 1.6527, no / 9.0995, 1.2496, no / 6.0967, 1.2598, no
4, 1.3407, 1.2595, no / 9.6348, 1.0726, No / 6.9007, 1.1557, no
5, 1.2304, 1.2556, no / 9.6348, 0.9018, yes / 6.9221, 0.9716, yes
6, 1.3433, 1.3534, no / 8.0373, 0.6439, yes / 4.3251, 0.4951, yes
7, 1.4179, 2.2177, no / 16.014, 1.3146, no / 11.145, 1.3066, no
8, 0.9138, 1.9275, no / 16.014, 1.3542, No / 11.247.1.3559, no
9, 0.6770, 1.7992, no / 14.782, 1.2500, no / 10.369, 1.2500, no
10, 0.5375, 1.7193, no / 14.782, 1.2500, no / 10.369, 1.2500, no
11, 0.4466, 1.6676, no / 14.782, 1.2500, no / 10.369, 1.2500, no
12, 0.3812, 1.6107, no / 14.782, 1.2500, No / 10.369, 1.2500, no 13, 0.3310, 1.5464, no / 14.782, 1.2500, no / 10.369, 1.2500, no
note 1: when SATWE software calculates "seismic shear force and seismic interlayer displacement ratio", fill in "0" in "relative stiffness ratio of backfill to basement restraint" in "basement information"
note 2: the number of weak layers and corresponding layer number are not defined separately in SATWE software
note 3: this example is mainly used to illustrate the realization process of the three stiffness ratios in SATWE software, and the rationality of the structural scheme is not discussed< (3) analysis of calculation results (1) the judgment results of weak layer are different when stiffness ratio is calculated by different methods
② in the "adjustment information" of SATWE software, the designer should specify the number of the sixth weak layer of the conversion layer. The designation of weak layer number does not affect the program's automatic judgment of other weak layers
③ when the transfer floor is set at three or more floors, the height regulation also stipulates that the lateral stiffness ratio of the floor should not be less than 60% of the adjacent upper floor. This SATWE software has no direct output results, so designers need to calculate the stiffness of each layer separately according to the program output. For example, the calculation results of this project are as follows:
1.3433 × 107／1.4179 × 107＝94.74％> 60%
meet the specification requirements< (4) whether the basement roof can be used as the embedded end of the superstructure:
A) the ratio of seismic shear force to seismic interlayer displacement
= 4.7283 × 107／1.7251 × The basement roof can be used as the embedded end of the superstructure
b) the shear stiffness ratio
= 11.444 × 107／9.0995 × (107) = 1.25 < 2
the roof of the basement can not be used as the embedded end of the superstructure
⑤ when SATWE software calculates the shear bending stiffness, the value range of H1 includes the height of the basement, and the height of H2 is equal to or less than H1. For the designers who want the value of H1 to be taken from 0.00 or above, or remove the basement and recalculate the shear bending stiffness, or manually calculate the stiffness ratio according to the shear bending stiffness output by the program. Taking the project as an example, H1 is calculated from 0.00, using the stiffness string model, the calculation results are as follows:
the floor number of the transfer floor is 6 (including basement), the starting and ending floor number of the lower part of the transfer floor is 3-6, H1 = 21.9m, the starting and ending floor number of the upper part of the transfer floor is 7-13, h2 = 21.0m.
K1 = [1 / (1 / 6.0967 + 1 / 6.9007 + 1 / 6.9221 + 1 / 4.3251)] × 107=1.4607 × 107
K2=[1/1/11.145+1/11.247+1/10.369 × 107=1.5132 × 107
Δ 1=1/K1 Δ 2 = 1 / K2
then shear bending stiffness ratio γ e= Δ one × H2/ Δ two × (6) discussion on the properties of three kinds of stiffness ratio
(1) ratio of seismic shear force to seismic interlayer displacement: a calculation method related to external force. Specified in the specification Δ UI includes not only the displacement caused by seismic force, but also the displacement caused by overturning moment Mi of the floor and the rigid body rotation displacement of the floor caused by the rotation of the next floor< (2) shear stiffness: the calculation method is mainly the ratio of shear area to the corresponding storey height, which is closely related to the shear area and storey height of vertical members. However, the shear stiffness does not consider the influence of the structural system with braces and the height of shear wall openings< (3) shear bending stiffness: actually, it is the interlayer displacement angle under the action of unit force, and its stiffness ratio is also the ratio of interlayer displacement angle. It can consider the influence of shear deformation and bending deformation at the same time, but does not consider the constraints of upper and lower layers
the properties of the three kinds of stiffness are completely different, and there is no necessary connection between them. Because of this, the code gives them different scope of application.
4. Earthquake load: (dizhenhezai) earthquake load (seismic force) also known as seismic force. Inertial force, earth pressure and water pressure on structures e to earthquake. Since the horizontal vibration has the greatest influence on buildings, only the horizontal vibration is considered. Calculation formula of seismic force: seismic force = self weight × Seismic coefficient. Compared with the steel-concrete structure, the self weight of the whole steel structure is lighter. The self weight of the steel structure is about two-thirds or one-half of the steel-concrete structure. According to the above calculation method, the steel structure building with light weight will greatly rece the seismic force, relieve the seismic force and protect the stability of the whole building.
5. Generally speaking, the calculation of seismic force is to analyze the influence of earthquake on buildings by mechanical method, which is a part of seismic design
in terms of specific calculation method, the calculation method stipulated in China's seismic code is to add the magnitude of seismic force corresponding to frequent earthquakes (i.e. earthquakes lower than the seismic fortification intensity, that is, the so-called "small earthquakes") to the building as a load to carry out seismic effect combination. Under these conditions, buildings are required to meet the requirements of bearing capacity limit and normal service limit
this is the design principle of "small earthquake is not bad" in seismic design
in fact, except for a few buildings specially designed for performance, for most other buildings, medium earthquake (that is, the seismic force corresponding to the fortification intensity) and large earthquake (the seismic force higher than the fortification intensity) are not calculated and analyzed, and are only guaranteed by structural measures, so as to achieve the design principles of "medium earthquake repairable" and "large earthquake does not collapse"
it is generally said that China's seismic design is "small earthquake design", so the safety performance is not well guaranteed ring large earthquakes, which is the main reason
only the structural members involved in earthquake resistance will be affected by earthquake force, such as frame beam column, shear wall, diagonal brace, etc. All the components mentioned in the code for seismic design (GB 50011-2010) belong to this category. All of these members may be reinforced e to the consideration of seismic action
the reason for "possible" is that seismic force is essentially a kind of horizontal force, and horizontal force is not only seismic force, but also wind. In the place with low fortification intensity, if the wind is strong and the house is high-rise, then it is likely that the effect of wind load is greater than the earthquake force. Whether to consider earthquake resistance has little influence on the calculation of reinforcement
as for the load combination, the seismic force is mainly combined with the gravity load, generally not with the wind load. For details, please refer to the code for seismic design (GB 50011-2010).
in terms of specific calculation method, the calculation method stipulated in China's seismic code is to add the magnitude of seismic force corresponding to frequent earthquakes (i.e. earthquakes lower than the seismic fortification intensity, that is, the so-called "small earthquakes") to the building as a load to carry out seismic effect combination. Under these conditions, buildings are required to meet the requirements of bearing capacity limit and normal service limit
this is the design principle of "small earthquake is not bad" in seismic design
in fact, except for a few buildings specially designed for performance, for most other buildings, medium earthquake (that is, the seismic force corresponding to the fortification intensity) and large earthquake (the seismic force higher than the fortification intensity) are not calculated and analyzed, and are only guaranteed by structural measures, so as to achieve the design principles of "medium earthquake repairable" and "large earthquake does not collapse"
it is generally said that China's seismic design is "small earthquake design", so the safety performance is not well guaranteed ring large earthquakes, which is the main reason
only the structural members involved in earthquake resistance will be affected by earthquake force, such as frame beam column, shear wall, diagonal brace, etc. All the components mentioned in the code for seismic design (GB 50011-2010) belong to this category. All of these members may be reinforced e to the consideration of seismic action
the reason for "possible" is that seismic force is essentially a kind of horizontal force, and horizontal force is not only seismic force, but also wind. In the place with low fortification intensity, if the wind is strong and the house is high-rise, then it is likely that the effect of wind load is greater than the earthquake force. Whether to consider earthquake resistance has little influence on the calculation of reinforcement
as for the load combination, the seismic force is mainly combined with the gravity load, generally not with the wind load. For details, please refer to the code for seismic design (GB 50011-2010).
6. Article 4.2.1 and 4.4.1 of the seismic code are the conditions for natural foundation and pile foundation not to carry out seismic calculation. I really don't know when to consider the wind load. Maybe high-rise buildings need to consider the wind load.
7. First of all, it should be clear that the bottom shear method is a simplification of the array decomposition response spectrum method, which regards the multi particle system as the equivalent single particle system. For the shear structure, only the first formation can be used. However, attention should be paid to the addition of horizontal seismic action in the final calculation.
8. The sum of standard value and variable load combination value of structure self weight. Variable load combination value, take variable load standard value * combination value coefficient
seismic action is usually calculated by mode decomposition response spectrum method. First, the finite element method is used to calculate the vibration modes and natural vibration periods of the structure, then the seismic influence coefficient and participation coefficient of each mode are calculated, and then the seismic action standard value of j-mode I particle is calculated according to fji
=
AJ
*
RJ
*
xji
*
GI
finally, the root mean square method is used to stack each fi to obtain the total FJ.
seismic action is usually calculated by mode decomposition response spectrum method. First, the finite element method is used to calculate the vibration modes and natural vibration periods of the structure, then the seismic influence coefficient and participation coefficient of each mode are calculated, and then the seismic action standard value of j-mode I particle is calculated according to fji
=
AJ
*
RJ
*
xji
*
GI
finally, the root mean square method is used to stack each fi to obtain the total FJ.
9. Excerpts from two paragraphs in SATWE's manual, see pages 14 and 27
when changing the parameter of "angle between horizontal force and global coordinate", the direction of seismic action and wind load will change at the same time, so it is recommended to use this parameter only when changing the direction of wind load. At this time, if the direction of the main axis of the structure is inconsistent with the direction of the new coordinate system, the angle of the main axis of the structure should be filled in as the "oblique lateral force additional seismic direction" to consider the seismic action along the main axis of the structure
if the direction of wind load is not changed and only the seismic action of other angles is considered, the angle between horizontal force and global coordinate does not need to be changed, and only the additional seismic action direction is added
according to Article 5.1.1 of the code for seismic resistance, when the intersection angle of oblique lateral force resisting members is greater than 15 degrees, the horizontal seismic action in the direction of each lateral force resisting member shall be calculated respectively
therefore, to sum up, I don't think it is necessary to backfill -87.59 degrees. Fill in when the angle to the orthogonal direction is greater than 15 degrees.
when changing the parameter of "angle between horizontal force and global coordinate", the direction of seismic action and wind load will change at the same time, so it is recommended to use this parameter only when changing the direction of wind load. At this time, if the direction of the main axis of the structure is inconsistent with the direction of the new coordinate system, the angle of the main axis of the structure should be filled in as the "oblique lateral force additional seismic direction" to consider the seismic action along the main axis of the structure
if the direction of wind load is not changed and only the seismic action of other angles is considered, the angle between horizontal force and global coordinate does not need to be changed, and only the additional seismic action direction is added
according to Article 5.1.1 of the code for seismic resistance, when the intersection angle of oblique lateral force resisting members is greater than 15 degrees, the horizontal seismic action in the direction of each lateral force resisting member shall be calculated respectively
therefore, to sum up, I don't think it is necessary to backfill -87.59 degrees. Fill in when the angle to the orthogonal direction is greater than 15 degrees.
10. The sum of standard value and variable load combination value of structure self weight. Variable load combination value, take variable load standard value * combination value coefficient
seismic action is usually calculated by mode decomposition response spectrum method. First, the finite element method is used to calculate the vibration modes and natural vibration periods of the structure, then the seismic influence coefficient and participation coefficient of each mode are calculated, and then the seismic action standard value of J mode I particle is calculated according to fji
=
AJ
*
RJ
*
xji
*
GI
finally, the root mean square method is used to stack each fi to get the total FJ.
seismic action is usually calculated by mode decomposition response spectrum method. First, the finite element method is used to calculate the vibration modes and natural vibration periods of the structure, then the seismic influence coefficient and participation coefficient of each mode are calculated, and then the seismic action standard value of J mode I particle is calculated according to fji
=
AJ
*
RJ
*
xji
*
GI
finally, the root mean square method is used to stack each fi to get the total FJ.
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